Wood boring bits such as augers are well known and are shown for example in the early Newton et al. U.S. Pat. No. 5,036 issued Mar. 27, 1847; the Whitehouse U.S. Pat. No. 364,153 issued May 31, 1887; the Bailey U.S. Pat. No. 413,159 issued Oct. 22, 1889, the Hoefle U.S. Pat. No. 430,344 issued June 17, 1890 and the Smith U.S. Pat. No. 597,750 issued Jan. 25, 1898.
Typically, these types of wood augers include a spiral shank terminating in a working end having typically for a single spiral bit, one generally axially extending and one radially extending cutting edge and for a double spiral bit, pairs of these cutting edges. The working end terminates in an integral non-cutting screw point or tip of very much smaller diameter than the diameter of the hole cutting edges, the screw point functioning to pull the bit into the workpart and to center the bit. Various problems have been encountered in manufacturing and using such wood augers, not the least of which is the tendency for the small diameter screw tip to break off in service, especially if the tip hits a nail in the wood being bored. Also, typically, the wood debris produced during boring with such augers is in the form of relatively large chips which must be removed from the hole by the spiral shank. As a result, the depth of the spiral is necessarily great to accommodate large size chips and convey them out of the hole. For a particular diameter hole, increases in spiral depth reduce the load bearing (cutting torque) cross-section of the auger, reducing the strength of the auger and sometimes necessitating heat treatment of the tip and spiral shank to provide added strength. When such augers are heat treated, there is a tendency for longitudinal warping which may cause rejection of the auger or which at a minimum requires straightening of the auger, a costly additional manufacturing step.
The Gaskins U.S. Pat. No. 3,824,026 issued July 16, 1974 illustrates an auger having a generally right triangular profiled lead end point on the working end to initiate cutting of the workpiece almost immediately upon contact therewith.
The Oakes U.S. Pat. No. 3,758,222 issued Sept. 11, 1973 describes a single longitudinally fluted bit which includes a series of stepped cylindrical sections increasing progressively in diameter from the tip toward the shank thereof. The single longitudinal flute provides a single cutting edge for each cylindrical section. This type of bit has been attached to the end of a spiral shank to form a so-called wood auger.